Learnings from the Texas nearshore dispersant demonstration project

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This project defines circumstances where a dispersant demonstration might be considered for an estuarine oil spill in Texas. In seeking approval for a spill of opportunity demonstration project, we developed criteria defining a viable dispersant response for consideration by the Region VI Regional Response Team. This paper presents the criteria and their rationale developed for Galveston Bay and Corpus Christi Bay, along with the results of recent training exercises. The criteria define the size and general location of an oil spill that might be considered appropriate for a trial dispersant application, and implementation of response and monitoring within a 2-hour window from notification. They are based on descriptions and characterizations of the habitats and species at risk in coastal areas, concentration and duration of dispersed oil plumes that might be generated in a response, potential impacts of these exposures, and the environmental trade-off between implementing mechanical response and a dispersant response. Because the dilution potential is constrained in shallow water environments, spill size has significant impact on the magnitude and duration of potential exposure regimes for water column organisms. Spills of 250 bbls or less pose minimal concern for water column communities with potential net benefit to other coastal resources. The trade-offs were not so obvious for larger spills. The exposure regimes and potential impacts for water-column organisms that would be maximally exposed during a dispersant operation were compared to the exposures and potential impacts for organisms and habitats exposed to floating oil and oil stranded on shorelines, at levels that could result during a mechanical recovery operation. These potential impacts are compared on a spatial and temporal basis, and with consideration for potential rates of recovery.